1. Field of the Invention
The present invention relates to a data scheduling module, a data scheduling method, and a computer program product thereof for a wireless communication apparatus. More particularly, the present invention relates to a data scheduling module, a data scheduling method, and a computer program product thereof for prolonging the sleep time of a wireless communication apparatus through data aggregation.
2. Descriptions of the Related Art
In terms of the range of coverage, wireless network schemes currently available fall into the following categories: the Wireless Wide Area Network (WWAN), the Wireless Metropolitan Area Network (WMAN), the Wireless Local Area Network (WLAN), the Bluetooth, the Infrared (IR) wireless network and various other wireless network standards. Among these wireless network standards, WLAN has the widest application in daily life, some examples of which are the WLAN access points (APs) that do not require physical wiring and WLAN wireless network cards for use in home computers.
Wireless networks have higher flexibility than wired networks in terms of both deployment and use. Meanwhile, the use of the wireless network may also substantially reduce the cost of manpower and materials associated with conventional wired networks. However, albeit these advantages, the wireless networks still suffer from a number of limitations, such as instable data transmission range, low data transmission security, slow data transmission speed, etc.
Over recent years, consumers' environmental awareness has increased. As a result, “power-saving” features are important to be considered during the early design stages of various electronic products. The design and production of electronic products related to wireless networks are of course no exception. For example, the IEEE802.16e wireless network standard has proposed three power-saving modes for the users' choice in achieving power-saving objectives.
According to the first power-saving mode, a mobile station presets an initial sleep window early at the beginning of data transmission. At the end of the initial sleep window, the mobile station will receive a broadcast message from the base station, informing the base station to either transmit or not transmit data to the mobile station. If the base station is to transmit data, the mobile station leaves from the sleep mode to communicate with and receive data from the base station. Otherwise, if the base station has no data to transmit, the mobile station will stay in the sleep mode by doubling the sleep window to extend the sleep duration, thereby achieving an improved power-saving effect. This power-saving mode is mainly applicable to such network applications, such as webpage browsing or data access.
According to the second power-saving mode, the mobile station presets a sleep window and a listen window of a fixed length early at the beginning of a data transmission. The mobile station then transmits data to or receives data from a base station at regular intervals according to the preset listen window of a fixed length and keeps silent in the sleep window. Unless the mobile station is actively requested to leave from the sleep mode, it will continuously stay in the sleep mode. With the nature of the fixed sleep window, this power-saving mode is mainly applicable to network applications in a real-time and periodic nature and with fixed data traffic such as Voice over Internet Protocol (VoIP) or video streaming network applications.
According to the third power-saving mode, before entering the sleep mode, a mobile station transmits a notification message to the base station so that the base station is informed whether the mobile station is going to enter the sleep mode and the desired duration of the current sleep window. Then the base station acknowledges the request with the duration of the sleep window. When the current sleep window expires, the mobile station leaves from the sleep mode to resume normal operations. Because the third power-saving mode does not have the same periodic nature as in the aforesaid two power-saving modes, this power-saving mode is mainly applicable to the periodic management of mobile stations by a base station, for example, instructing a mobile station to make signal adjustments consistent with the base station at regular intervals.
FIG. 1 depicts the wireless network 1 of a prior art conforming to the IEEE802.16e wireless network standard and adopting the second power-saving mode described above. The wireless network 1 comprises a base station 101, a first mobile station 103 and a second mobile station 105. FIG. 2 is a schematic view illustrating data transmission between the base station 101 and the first mobile station 103. The base station 101 is going to transmit a plurality of data A, B, C, D, E of a first connection 201 and a plurality of data F, G, H of a second connection 203 to the first mobile station 103, in which the data A, B, C, D, E of the first connection 201 and the data F, G, H of the second connection 203 are both to be transmitted in a plurality of frames I, II, III, . . . , IX.
In particular, the base station 101 will transmit the plurality of data A, B, C, D, E in frames I, III, V, VII, IX at an interval of two frames (i.e. the data transmission interval is two frames), and transmit the plurality of data F, G, H in frames I, V, IX at an interval of four frames (i.e. the data transmission interval is four frames). Then, the base station 101 integrates the data A, B, C, . . . , H of the first connection 201 and the second connection 203 into a first time arrangement 205. Accordingly, the base station 101 will transmit the data A and F in frame I, the data B in frame III, the data C and G in frame V, the data D in frame VII, and the data E and H in frame IX.
Meanwhile, according to the aforesaid calculation results, the first mobile station 103 will have the antenna module powered off during the unused frames (i.e. frames II, IV, VI, VIII) of the first time arrangement 205.
FIG. 3 is a schematic view illustrating the data transmission between the base station 101 and the second mobile station 105. The base station 101 is going to transmit a plurality of data a, b, c, . . . , i of a third connection 301 and a plurality of data j, k, l, m, n of a fourth connection 303 to the second mobile station 105, in which the data a, b, c, . . . , i of the third connection 301 and the data j, k, l, m, n of the fourth connection 303 are also to be transmitted in the plurality of frames I, II, III, . . . , IX.
In particular, the base station 101 will transmit the plurality of data a, b, c, . . . , i in frames I, II, III, . . . , IX at an interval of one frame (i.e. the data transmission interval is one frame), and transmit the plurality of data j, k, l, m, n in frames I, III, V, VII, IX at an interval of two frames (i.e. the data transmission interval is two frames). Then, the base station 101 integrates the data a, b, c, . . . , n of the third connection 301 and the fourth connection 303 into a second time arrangement 305. Accordingly, the base station 101 will transmit the data a and j in frame I, the data b in frame II, the data c and k in frame III, the data d in frame IV, the data e and l in frame V, the data f in frame VI, the data g and m in frame VII, the data h in frame VIII, and the data i and n in frame IX.
Meanwhile, according to the aforesaid calculation results, no frame is left unused in the second time arrangement 305, so the second mobile station 105 is not allowed to power off the antenna module thereof.
According to the above descriptions, as long as there is data to transmit in a frame, the mobile station will have to power on the antenna module thereof for a fixed duration for data transmission purpose regardless of the size of the data. Therefore, the power of the mobile station will be excessively consumed if the data is fragmental. For example, in the first time arrangement 205 of the first mobile station 103, the amount of data transmitted in the frames III and VII is very small. Likewise, in the second time arrangement 305 of the second mobile station 105, the amount of data transmitted in the frames II, IV, VI and VIII is also very small. Even with such fragmentary data, the mobile stations 103, 105 still have to power on their antenna modules for a fixed duration for data transmission purpose, causing significant degradation of the power-saving effect.
On the other hand, when transmitting the data A, B, C, . . . , H of the first mobile station 103 and the data a, b, c, . . . , n of the second mobile station 105, the base station 101 processes the data A, B, C, . . . , H and a, b, c, . . . , n simultaneously depending on the data transmission capacity of the frames. As shown in FIG. 4, during the processing of all the aforesaid data, the base station 101 has to process an amount of data A, F, a, j in frame I that exceeds the data transmission capacity of the frame; an amount of data C, G, e, l in frame V that exceeds the data transmission capacity of the frame; and an amount of data E, H, i, n in frame IX that exceeds the data transmission capacity of the frame. When such a case occurs, the data j intended to be transmitted in frame I, the data l intended to be transmitted in frame V and the data n intended to be transmitted in frame IX will fail to be processed by the base station 101, causing a failure in the scheduling operation of the base station 101. As a consequence, the base station 101 has to force the first mobile station 103 or the second mobile station 105 to leave the power-saving mode, making it difficult to save power in the wireless network 1.
According to the above descriptions, the wireless network 1 of the prior art conforming to the IEEE 802.16e wireless network standard and adopting the second power-saving mode suffers from the following two drawbacks:                1. If there is data to transmit in frames corresponding to several connections of a single mobile station, the mobile station has to power on the antenna module thereof for a fixed duration for data transmission purpose regardless of the size of the data. If the data to be transmitted is insufficient to occupy the whole time window when the antenna module is powered on, the power of the mobile station will be excessively consumed in an idle status. As a result, there is a significant degradation of the power-saving effect.        2. When the number of mobile stations associated with a single base station increases, the data amount the base station processes will also increase considerably to cause a failure in the scheduling operation of the base station 101. This would force some of the mobile stations to leave the sleep mode to result in increased power consumption.        
Accordingly, efforts still have to be made by the network equipment manufacturers and network service providers to improve the utilization factor of frames in the wireless networks and enhance the capability of a base station to process data of a plurality of mobile stations by solving the aforesaid two problems with the wireless networks conforming to the IEEE 802.16e wireless network standard and adopting the second power-saving mode.